Fr. James Brent O.P. does an excellent job of summarizing, explaining, and defending a contingency argument found in Aquinas’ Summa Contra Gentiles, Book two, chapter 15.

Here’s the text of Aquinas:

Again, everything that can be and not-be has a cause; for considered in itself it is indifferent to either, so that something else must exist which determines it to one. Since, then, it is impossible to go on to infinity, there must exist a necessary being which is the cause of all things that can he and not-be. Now, there is a certain kind of necessary being whose necessity is caused. But in this order of things, also, progression to infinity is impossible; so that we must conclude to the existence of something which is of itself necessary being. There can be but one such being, as we proved in Book I. And this being is God. Everything other than God, therefore, must be referred to Him as the cause of its being. [Source]

Argument Outline

Fr. James Brent O.P. organizes the argument as follows:

1. Contingent beings exist.
2. Every contingent being receives its existence.
3. It’s impossible to proceed to infinity in a series of contingent beings, each of which receives its existence.
4. There must be a necessary being that gives existence to contingent beings.
5. There is only one such necessary being.

That’s a brief outline. However, Fr. Brent devotes most of the talk to defending each premise carefully and logically. I listened to this in the car ride home the other day; Fr. Brent blew me away with his clarity. At the end of the talk, he discusses three objections.

First objection: That conclusion is not God.

Second objection: The conclusion is not the God of the Bible.

Third objection: Premise 2 is false since there are some contingent beings that are brute facts.

Enjoy the Lecture!

 

One strength of a contingency argument, as opposed to the Kalam argument, is that it works even if the universe is eternal. Also, once the terms of the premises are explained, they are extremely reasonable. At the very least, it is rational to hold all of them, which means it is rational to hold the conclusion.

For an even more detailed treatment of a contingency argument, check out chapter 5 of Dr. Feser’s Five Proofs of the Existence of God.